There are power converters that convert DC power generated by a solar cell into AC power. For example, JP 2005-341680A discloses a power controller in a system interconnection system that outputs power output by a DC power supply to a power system. The power controller of JP 2005-341680A includes measurement means for measuring the impedance of the power system, setting means for setting a control parameter relating to power that is output to the power system, based on the measured impedance, and control means for controlling power that is output to the power system using the control parameter. As a result of this configuration, an increase in system voltage is reliably and stably suppressed, and the power generation efficiency and capacity factor are enhanced in the system interconnection system.
JP 2005-341680A is an example of background art.
Generally, a power converter is connected to a system (specifically, pole transformer) via wiring. This wiring has impedance (hereinafter, “system impedance”). In order to perform stable control in a power converter interconnected to a system, it is necessary to set control parameters with consideration for this system impedance. However, the system impedance value changes depending on the length of the wiring, and differs according to the environment in which the power converter is installed.
When designing power converters, it is difficult to gauge the system impedance value of future installation environments beforehand. Thus, heretofore, there were concerns about control becoming unstable in response to the system impedance, and power converters were designed with a margin built into the inductance value of the smoothing inductor for the AC output voltage with consideration for the maximum impedance value that was envisaged. This resulted in increases in the component size and the cost of power converters.